The technology provided herein relates to the rapid separation and collection of particles suspended in a fluid and more particularly relates to the rapid separation of bacteria from blood to be used for diagnosis of blood infections.
Suspended particles of similar density are very difficult to separate from each other by isopycnic centrifugation. If their sizes are slightly different, separation by filtering becomes challenging particularly if the smaller sized particle is also in the minority by number, as the high number of large particles will block the filter pores and prevent many of the small particles from passing. There are methods such as cross-flow filtration in which the large particles are swept laterally away from the pores so the small particles can pass; however this method is often time consuming and requires large volumes of fluid for the cross-flow filtration process. In cases with requirements of rapid separation with very little process fluid, sedimentation remains a convenient process that can separate particles of similar density and slightly different size, even when the small particles are in the vast minority. While sedimentation can be used to separate any set of particles that have differing sedimentation velocities, sedimentation is particularly useful to separate smaller bacteria in concentrations of hundreds per milliliter from slightly larger red blood cells in concentrations of billions per milliliter, in a rapid manner without requiring or producing large amounts of excess liquid.